The main purpose of this protocol is to redefine threonine minimum dietary requirement intake. To assess the adequacy of threonine in the diet, leucine will be ued as indicator amino acid. 24-h leucine oxidation will be measured after 7 and 14 day period of adaptation to different intakes of threonine. We hypothesize that leucine oxidation will balance leucine intake in response to a threonine intake of 15 mg/kg-1.d-1 (adequate threonine diet). On the opposite, at the current FAO/WHO/UNU threonine requirement, 7 mg/kg-1.d-1 (low threonine diet), a negative leucine balance is expected. Leucine oxidation will be lower than leucine intake, in response to a diet generous in threonine, resulting in positive leucine balance.